These Medieval Arming Caps were used during Medieval times under helmets to protect the wear's head. The arming cap is a great addition to any of our Medieval helmets. Helmet designs in the Middle Ages focused on function, and their function was to provide protection against large, heavy weapons used in close combat. This Cloth Helmet Liner would have been a must-have to anyone spending any length of time donning a metal helmet on horseback. One size fits all.